Awhile back I put out an information request for a BRIGHTNESS problem I was having on my WD-57831, although I never seemed to get a response on it. Since this problem occured over-night, I was prettty convinced it was an electrical fault and went at it with that train of thought. After spending a few weeks of tear'n it down and tracing every related circuit I could think of, I finally just went ahead and cleaned every lens,mirror, prisim along with the color wheel, but that didn't seem to help at first.
After I had pulled the LIGHT TUNNEL out for about the third time, I noticed that 1 of the mirrors had dis-attached from the side and was laying flat on the bottom mirror. Since these mirror pieces are small and the reflective side was face up, it was easy to miss it at first. After I lifted the piece up, I found some particles underneath it... maybe leftovers from a dryed out adhesive that held the mirror in place. After I got the mirror piece pack in place, cleaned it and then put everything back together, tthe picture is GREAT!. After cleaning every lens and such, it looks like it just came out of the box!